Radio-frequency antenna



FIG. 1 is a perspective view of the radio-frequency antenna;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The portions shown in dotted lines do not form part of the claimed design. 

CLAIM The ornamental design of a radio-frequency antenna, as shown and described. 